When the light hits the surface of the skin, it separates into two components: a transmitted component and a reflected component. The transmitted light is itself divided into a component of specular or direct transmission (at a single angle) and a component of diffuse transmission (in all directions). The reflected light is also divided into a component of diffuse reflection (in all directions) and a component of specular reflection (at a single angle).
It is known that, depending on their size, shape and chemical nature, pulverulent materials interfere with the various components of light above and as a result have the capacity to modify the appearance of the skin.
Research has become focused in recent years on powders with high diffuse reflectance, low specular reflectance and high diffuse transmittance, which make it possible especially to reduce the appearance of wrinkles and fine lines by reducing the difference in luminosity between the valley and the edges of wrinkles.
These powders, known as “soft-focus” powders, also make it possible to give shiny skins a more matt appearance.
Now, obtaining a matt effect on the skin is highly sought by users with combination or greasy skin, and also for cosmetic compositions intended to be used in hot and humid climates. The reason for this is that the highlights caused by an excess of sebum on the surface of the skin are generally considered as unattractive.
Among the soft-focus powders proposed in the prior art, mention may be made of certain micas coated with minerals and/or with PMMA, optionally coated silica microspheres, nylon powders, boron nitride, or talc with a granulometry (or mean particle size) of 1.8 microns.
It nevertheless remains that there is still a need for materials that allow the surface defects of the skin to be camouflaged.